GB1134654A - Synchronization signal comparison system - Google Patents

Abstract

1,134,654. Monitoring tuning of television receivers; transistor monostable circuits. A. C. NIELSON CO. 23 March, 1966 [29 March, 1965], No. 12872/66. Headings H3T and H4L. Horizontal and vertical synchronizing pulses obtained from a monitored television receiver at terminals 26 and 28, Fig. 1, are compared with corresponding pulses obtained from a reference receiver at terminals 22 and 24 with the aid of coincidence gates 30 and 34 and the gate outputs are applied to control an indicator or recorder 42 by way of a further coincidence gate 38, multivibrator 40 and integrator 41, the arrangement being such that an indication or record is produced only when both the horizontal and vertical synchronizing pulses from the two receivers are in phase. The arrangement is intended for audience survey purposes and serves to indicate whether a monitored receiver is tuned to receive the same channel as the reference receiver. The horizontal sunchronizing pulses may be derived from the picture tube cathode circuit or horizontal scanning oscillator whilst the vertical synchronizing signals may be derived from the vertical scanning oscillator. Reference is also made to means (not described) for receiving the signals from the monitored receiver remotely. Detailed transistor circuits for units 30, 32, 34, 36 and 38 are described with reference to Figs. 2-4 (not shown). Multivibrator 40 comprises a circuit as shown in Fig. 5 in which the multivibrator pair 134, 136 is reset after being triggered in response to a pulse at terminal 128 by a unijunction transistor 164 which is itself triggered after a time primarily determined by C.R. circuit 166, 168.